Psychic channeling is a way to interact with psychic energies within yourself that you haven't accepted as your own.
As far as the psychic realm is concerned, the whole world is within us. We can 'resonate' or relate to any part of the world or differing state of consciousness - albeit most of the time not very effectively.
Understanding something completely means accepting that something completely. There is a downside; for example, if you want to accept the Sun completely you will get burned to ashes long before even you get near it.
Through psychic channeling you can carve out a 'channel' within yourself through which the dangerous, differing energies can pass through - and isolate that channel of energy within enough so that you interact with it in only a limited manner.
Needless to say, although the rewards can be plentiful, psychic channeling has its dangers. If you insist on becoming a psychic channel, proceed only if you have a great deal of balance, self-discipline and can exercise a great deal of caution.